Many aspects of human physiology can be monitored by electronic monitoring devices. For example, the electrical activity of a patient's brain can be monitored by an electroencephalograph (EEG). Similarly, the electrical activity of a patient's heart can be monitored by an electrocardiograph (ECG). Electronic monitoring by these devices requires the application of one or more sensing electrodes to the patient.
For example, ECG monitoring involves the application of a number of precordial electrodes that are attached to the torso of the patient, and/or limb electrodes that are attached to the limbs of the patient. Electrical activity can be monitored using both the limb electrodes and the precordial electrodes as part of a 12-lead ECG analysis (requiring six electrodes), or using the limb electrodes alone as part of a 3-lead ECG analysis (requiring four electrodes).
Generally, the four limb electrodes are connected via separate electrical conductors to a common limb connector. The six precordial electrodes are connected via separate electrical conductors to a common precordial connector. These connectors are coupled to the ECG monitor. Collectively, the electrodes, conductors and connectors are referred to as lead assemblies.
In most emergency or trauma situations, an attending physician or medical technician is interested in viewing a three-lead ECG signal. The three-lead ECG signal is used in determining what emergency drugs may need to be administered or whether the patient needs to be defibrillated. Twelve-lead ECG signals are most often used in diagnosing the presence or absence of heart disease during nonemergency conditions.
In order to reduce the number of cables that must be connected between the ECG monitor and patient, some ECG lead assemblies are combined such that the four limb electrodes/cable and six precordial electrodes/cable are connected via a separate single multiconductor cable to the ECG monitor. When a standard three-lead ECG signal is desired, the precordial electrodes/cable can be disconnected from the ECG monitor without affecting the connection of the limb electrodes/cable.
With combination lead assemblies, it is important that the connection of the electrodes be intuitive and simple. For example, in emergency situations a physician should not have to guess how the electrodes are connected to the lead assembly. Additionally, there can be problems if the assembly has exposed connection sites. Fluids, such as blood or intravenous medicines, may be accidentally splashed onto an exposed connection site, thereby corroding or short-circuiting conductive elements in the connector. Moreover, dirt particles may accumulate at the exposed connection site, obstructing subsequent connections of the electrode connectors and/or increasing the electrical impedance of the connections. All of these effects may prevent the ECG monitor from correctly sensing electrical activity occurring under the electrodes.